Petroleum-based materials are integral to the world's economy and demand for petroleum based fuels and petroleum based products is increasing. As the demand rises, there is a need to efficiently and economically process petroleum-based materials to fulfill that demand. As such, it would be advantageous to not only be able to process raw petroleum-based materials from the earth, but to recycle consumer products to recapture those petroleum-based materials.
Worldwide oil consumption is estimated at in excess of seventy million barrels per day and growing. Thus, there is a need for sufficient oil supplies. Tar sands, oil sands and oil shales, contain large quantities of oil; however, extraction of oil from these materials is costly and time-consuming.
Pumping heavy oil from oil sands is difficult. Typically, up to 30% by volume of a solvent or diluent must be added to such oil to make it thin enough to pump through pipelines. This adds a cost of as much as 15% to a barrel of oil at current prices. Thus, the ability to economically break some of the molecular bonds to make the oil less viscous could have a significant impact on the recovery of useful products from oil sands. Another problem that is becoming increasingly important is the disposal of toxic wastes. Generally to render wastes harmless requires breaking chemical bonds in the waste and possibly then adding other substances to form new bonds.
In prior art, it is known that a process or reaction volume can be excited in a resonant electromagnetic structure with an electromagnetic generator coupled to it. The structure is generally multimode (i.e., multi-spatial mode). A microwave oven is an example of such an apparatus.
The resonant structure also may be a single mode structure, wherein a single frequency is resonant in a single spatial mode. A single mode resonant structure is smaller than a multimode resonant structure and cannot handle as much power input. In many applications, it is desirable to create a plasma in a process or reaction volume, and it is generally easier in a single mode resonant structure to establish a stable plasma and to maintain matching to the generator and its delivery system.
It also is known that a reaction or process volume can be excited in a multimode resonant structure coupled to a plurality of electromagnetic generators. For example, U.S. Pat. No. 7,227,097 describes a system using multiple generators coupled to a common multimode resonant structure, with a plasma created in the common resonant cavity. This configuration has the advantage of permitting more input power, but the multimode cavity is far more sensitive to plasma fluctuations. Matching and maintaining the electromagnetic generators and their respective delivery systems also is difficult in this configuration. There also is more cross-coupling of the various generators through plasma instabilities. Prior art references also provide multiple generator inputs for a single mode resonant structure, but in the single mode configuration each generator would be required to have the same frequency and phase, and the resonant structure would limit how much power could be applied.
In many cases, it is necessary to use very high frequencies, for example microwaves. Generation of microwave energy (roughly 300 MHz to 300 GHz) from input electrical energy is typically only about 50 to 70% efficient. By comparison, generation of lower radio frequency (roughly 455 KHz to 300 MHz) energy conversion is up to 95% efficient.
In some processes or reactions, it becomes necessary to use microwave energy. For example, in many applications it is necessary to form a plasma using microwave frequencies, but it would be very advantageous to further heat the plasma using lower frequencies that can be generated more efficiently. Further, in a microwave resonant structure, generally the plasma is not uniformly heated along the length of a process or reaction chamber.
Accordingly, there is a need for an improved method and apparatus for treating a process volume with increased efficiency. Specifically, it is desirable to excite the plasma uniformly along the length of the reaction chamber and to utilize lower radio frequency energy conversion.